Design of a new family of catalytic support based on thiol containing plasma polymer films Dr. D. Thiry damien.thiry@umons.ac.be Chimie des Interactions Plasma Surface (ChIPS), CIRMAP, University of Mons, Belgium Materia Nova Research Center, Mons, Belgium
Introduction Supported gold nanoparticles for catalysis Catalytic activity discovered by Haruta in 1982 (Nanoparticles size : 2-5 nm) L-F. Gutierrez et al, Catalysis, 2011, 1, 97 High activity towards CO oxidation event at room temperature (1-4) Better selectivity for the oxidation of organic compounds (1-4) Applications Control of car pollution (Oxidation of CO, reduction of NO x, ) Synthesis of organic compounds (Ex. Epoxypropene) Control of air quality (Oxidation of volatile organic compounds) (1) C. Della Pina et al., Chem. Soc. Rev., 2008, 37, 2077 (2) Min et al,chem. Rev., 2007, 107, 2709 (3) C.Louis, L actualité chimique, 2005, 282, 48 (4) A. Corma et al, Chem. Soc. Rev., 2008, 37, 2096 2
Catalytic activity (Arb. Unit) Introduction But Decrease in catalytic activity with time (1-3) Adapted from M. Chen et al, Chem. Soc. Rev. 2008,37,1860 Gold nanoparticles Gold nanoparticles Agglomeration of the nanoparticles S S S Support 10 nm 10 nm Before the reaction After the reaction The presence of thiol supporting functions could improve the stability of the supported gold nanoparticles (4) (1) M. Valden et al, Cat. Letters, 1998,56,7 (2) T. Choudhary et al, Top. Catal., 2002, 47, 25 (3) P. Konova et al, Cat. Comm., 2004, 5, 537 (4) S. Li et al, Macromol. Chem. Phys., 2005,26,1967 Reaction Time (min.) : Gold Nanoparticles 3
Introduction FPP-50 W Synthesis method? FPP-100 W Nowadays, typically, these surfaces are synthesized by wet chemistry strategies (1,2) but these methods are (i) substrate-dependent and (ii) make necessary the activation of the exposed surface The plasma polymerization of a thiol-based precursor might be an efficient alternative because Substrate-independent method To Environmentally evaluate friendly the potential of thiol-containing plasma The film properties can be modulated polymer by adjusting films the process as a parameters stabilizing support for gold nanoparticles Well established industrial transfer SH SH SH Plasma Polymer Film Substrate (1) E.A. Smith et al, Langmuir, 2001, 17, 2502 (2) A. Niklewski et al, Langmuir, 2004, 20, 8620 4
Introduction Growth mechanism Plasma = Initiator of polymerization CH 3 CH 2 CH 2 SH CH 3. CH 3 CH 2 CH 2 SH. H 2 S CH 2 -CH 2 -SH SH. hν e - CH 3 -CH 2. H 2 H. e - CH 3 +. CH 2 -SH v. CH 2 -SH. CH 3 -CH 2 CH 3 + hν Conventional polymer Good mechanical properties Thermal stability Plasma polymer The concentration of the chemical group of interest needs to be optimized Plasma Substrate Polymer Thin Film 5
Experimental set-up Precursor : Propanethiol Silicon substrate (Floating Potential) Precursor flow rate = 10 sccm Working pressure = 40 mtorr ICP plasma around a copper coil located inside the chamber Studied Parameter : 14 W < <P> < 100W 6
Results Plasma Polymerization of propanethiol Increase in the deposition rate with the energy dissipated in the discharge The thiol concentration is nearly constant in our experimental window 7
Results Synthesis of gold nanoparticles? Magnetron sputtering CATHODE - Gold Species Argon Ion N Gold Target S N Plasma Ar ANODE + Plasma Substrate Polymer Thin Film 8
Results Morphology of nanoparticles? TEM image Mean diameter = 4.1 nm Std = 2.9 nm Well dispersed and nearly spherical gold nanoparticles Adequate size for attractive chemical and optical properties (1) 9
Results Stability of the composite? In-situ annealing experiments in the microscope XPS Before gold deposit Temperature SCH 3 SH SH Plasma Polymer Substrate As-Measured After gold deposit T = 60 C T = 160 C Formation of bond between S and Au S S S Plasma Polymer Substrate Mean Diameter = 4.1 nm Std = 2.9 nm Mean Diameter = 4.2 nm Std = 2.9 nm 2 0 n m Mean Diameter = 4.3 nm Std = 3 nm Good stability of the composite material in the investigated range of temperature 10
Conclusions Conclusions Encouraging results have been obtained concerning the use of propanethiol plasma polymer as a support for gold nanoparticles Our developed approach is advantageous in many aspects: Substrate independent Solvent-free Stabilizing support and gold nanoparticles synthesized in two steps in the same reactor Thank you for your attention 11